Diagnosis of Early Gastric Cancer Aided by Optimal Band Imaging

Gastric cancer is one of the most prevalent types of cancer in the world. If gastric cancer is found early, the five-year survival rate increases nearly 90%. In contrast, most patients with advanced gastric cancer have a poor prognosis. Gastric cancer is classified as elevated, flat, and depressed types. In spite of improvements in endoscopic technologies, depressed-type early gastric cancer is challenging to diagnose because it manifests as slight alterations in color and shape. Variations in color, however, can also mean inflammation, so it is difficult to determine what is benign and what is malignant. Therefore, biopsies must then be taken.

"In our comparative study, the optimal band imaging system with endoscopy showed contrasting images that could delineate the depressed-type early gastric cancers more easily than conventional endoscopy,” said the study's lead author Hiroyuki Osawa, M.D., Jichi Medical University (Tochigi-Ken, Japan). "A distinct demarcation was observed endoscopically between the reddish images of the cancerous lesion and the yellowish images of the surrounding noncancerous area. This is the first report of optimal band images for early gastric cancer.”

Optimal band imaging (OBI) was developed with the goal of enhancing the capillary pattern and pit patterns of lesions in endoscopic images. In contrast to narrow band imaging, in which the bandwidth of spectral transmittance is narrowed by optical filters, the OBI system is based on a new spectral estimation technique that replaces the need for optical filters. OBI takes an ordinary endoscopic image from the video processor and arithmetically processes the reflected photons to reconstitute virtual images for a choice of different wavelengths.

An OBI system with electronic endoscope for the upper-gastrointestinal tract was used in this prospective study. Twenty-seven patients between May and December 2006 who were diagnosed with conventional endoscopy as having depressed-type early gastric cancer participated in the study. The mean age of the patients was 65.3 years with 23 men and 4 women. Twenty-four patients were diagnosed with differentiated adenocarcinoma and three patients with undifferentiated adenocarcinoma by the histopathologic evaluation of biopsy specimens. Researchers used the OBI system without magnification to observe the entire stomach because of the ample light intensity.

With the OBI system, depressed type-early gastric cancer in 26 of 27 cases were easily identified because it clearly showed contrasting demarcation lines between the reddish images of the cancerous lesions and the yellowish images of the surrounding noncancerous area. A 40-fold magnification was then applied to observe the pit pattern, the disappearance of pit pattern, or an irregular microvascular pattern of the cancerous lesions, which further enhanced the demarcation of the cancer and the noncancerous areas.

The researchers concluded that OBI images were better than traditional endoscopy images in identifying depressed-type early gastric cancer, but said that additional study is needed. They noted that even medical students, who had not had considerable amounts of clinical endoscopic experience, were able to easily identify the demarcation line between cancer and noncancerous areas in optimal band images versus conventional endoscopic images. OBI is available even without magnification during routine endoscopy because the system provides the same light intensity as conventional endoscopy. The researchers reported that such nonmagnified optimal band images might be ideal for screening, whereas magnified optimal band images are more suitable for detailed examination of early gastric cancer.

Endoscopy is performed by specially trained physicians called endoscopists using the most current technology to diagnose and treat diseases of the gastrointestinal tract. Using flexible, thin tubes called endoscopes, endoscopists are able to access the human digestive tract without incisions via natural orifices. Endoscopes are designed with high-intensity lighting and fitted with precision devices that allow viewing and treatment of the gastrointestinal system. In many cases, screening or treatment of conditions can be delivered via the endoscope without the need for further sedation, treatment or hospital stay.

The study was published in the February 2008 issue of Gastrointestinal Endoscopy.


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